Ice Dams Prevention & Ventilation of Low-Slope Roofs (2023)


Ice Dams can cause very serious and expensive to fix problems, and are usually caused by improper ventilation of your attic space and inadequate insulation of your roof. Ice Dams are a sign of heat loss in the attic, and this lost heat is money you throw out the window.

Ice dams may seem harmless at first, but they are known to cause thousands of dollars in roof leaks, structural damages and repairs of your home. The can also create dangerous mold growth, which can cause or aggravate allergies, asthma and other respiratory diseases. Fighting ice dams can be costly, and you also need to know how to approach the problem to make your efforts more efficient so that you can permanently eliminate them.

This Ice Dams Prevention Guide will help you identify Ice Dams and eliminate either sources of the problem (preferred method, though not always feasible) or the effects, which are just as dangerous for you home.

What are Ice Dams?

Ice Dams Prevention & Ventilation of Low-Slope Roofs (1)

If you live in Northern US, Canada, or any other region with cold winters and lots of snow, you’ve seen and possibly experienced first hand Ice Dams – large ice formations along the eaves of the roofs. Although ice dams are common on most roofs in the northern regions of US and Canada, they cause most damages and leaks to Low Slope roofs, as it is much easier for water to “travel” up a low pitch roof vs. a steep roof.

Additionally, you may see many roofs in New Hampshire, northern Massachusetts, as well as other parts of the country with 2 x 2 feet aluminum pans locked together along the eaves of the roof. These metal sheets are installed so that ice formations would slide off, and ice dams would not build up. This may work for steep roofs, but on a low slope, the ice dams can form in the center of the roof as there is not enough pitch for water to run off.

Just a few of the most common ice dam related problems include roof leaks, rotted roof decking / exterior & interior walls / framing, mold and related respiratory illnesses (allergies, asthma, etc.), reduction in insulation effectiveness and associated heat-loss.

(Video) What you should be doing to prevent ice dams forming on your roof

What Causes Ice Dams?

The main causes of ice dams are poor ventilation and / or inadequate insulation in the attic. When it snows outside, a thick layer of snow settles on the roof, and the warm air from the attic slowly melts the snow. Melted snow begins to run down the roof toward the eaves, which are usually colder than the rest of roof surface. There, water freezes, thus creating ice dams. As more and more water melts at the top of the roof and freezes at the bottom, ice dams grow to a thickness of over 4-5 inches.

As ice dams become larger, and more melted snow water runs down the roof, it hits the already large ice dams and can not go down any more. At this point it starts to refreeze under the shingles. At the same time, warm attic air melts the newly formed ice under the shingles, which starts to drip inside the attic and /or down the walls.

Ice Dams and Ventilation

Even if you have a very well insulated attic, which blocks most of the warm air from escaping your living space, still, some warm air will escape into the attic. This is where you need a working ventilation system, which will vent most of the warm air from the attic and will create temperature parity between outside and inside the attic. Only then, the snow will not melt artificially, and will not create ice dams.

Ice Dams Prevention & Ventilation of Low-Slope Roofs (3)

(Video) How to Treat and Prevent Ice Dams | Ask This Old House

Today, the most effective and commonly used attic ventilation system in residential construction and roofing is the Soffit / Ridge vent system. Although soffit/ridge system is the best-performing type of ventilation, it is not always possible to install it. While installing a good ventilation system on a new construction home is easy, some of the older homes were designed to have no ventilation at all, or optionally were build with two gable vents that are usually two 12 x 18 inches openings at the peak of the gable-side walls. These are not as effective as ridge and soffit vents but still work O.K.

In many cases however having a ventilation system is not an option due to many reasons, such as financial constraints or building limitations. For example, if a home was build with insulation stuffed between the roof rafters, but the the builder did not install baffles, which would create an air pocket to allow the flow of air. In this case no ventilation system will work, as there is no room for air to circulate. Of course, this situation can be fixed, but it would cost a lot of money and many homeowners are unwilling to spend that much.

Other types of roofs that are not designed to accommodate effective ventilation systems, such as ridge / soffit vents or gable vents, are Hip Roofs and low slope roofs. In the case of hip roofs, you could get away with static box vents or power vents with a thermostat. These are not as effective, but still provide some ventilation.


Ice Dams Prevention & Ventilation of Low-Slope Roofs (4)

In the case of low slope roofs, builders and roofers not only need to solve the ventilation problems, but they also have to make sure that there are no leaks caused by the air vents. Unfortunately, too many builders and roofers do not include any ventilation on a low slope roof, as it is easier for them to avoid potential leaks. For example, a ridge vent on a low pitch roof will allow the wind driven water to enter the attic.

Since most low slope roofs are not vented, ice dams are much more likely to occur and cause extensive damages to the roof and the interior of the house, as it is a lot easier for water to travel “upward” on a low pitch roof. Most low slope and flat roofing systems are designed to have their seams put together with glues and adhesives, ranging from solvent based seam lap adhesives used with EPDM black rubber to Tar and roof cement used with asphalt and modified bitumen roofs. Du to the nature of adhesives, these roofs are prone to develop leaks, as adhesives break down with time and weather affecting their longevity. Ice Dams only speed up the process, as the ice melting and re-freezing process expands the gaps between the seams.

Additionally, asphalt shingles are often used on low slope roofs, which is blunt ignorance on the part of homeowners, who did not do the due diligence, and hired a roofing contractor to install such a roof, as well as homeowner abuse by shady roofing contractors, who do not let their client know that the roof they are about to install violates manufacturers installation guidelines and annuls the warranty on the roof. By definition, a low slope roof has a pitch pf less than 3, while ALL shingles manufacturers require at least a pitch of 3 to install their asphalt shingles product.

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(Video) Ice Dam Prevention - low-slope roofing membrane we installed in Hingham, MA

Heat Cables DO NOT Solve Ice Dam Problems

In many cases, homeowners with low sloped roofs, turn to heated electric cables to melt the ice dams. Despite common opinion that heat cables solve ice dam problems, it could not be further from truth.

First, just a reminder that ice dams are caused by hot air escaping your living space and lack of adequate ventilation. Heat cables use electricity to melt the ice formations. Therefore, you are trying to fight a heat / energy problem by throwing more energy into the cold atmosphere, so instead of fixing the problem you just add a band-aid, which does not even work. At the same time, you incur ever increasing energy expenses, while the problem not only remains there, but becomes worse.

Heat cables melt ice dams along the eaves, but there are still ice dams forming just above the effective range of heat cables, so your ice dam leaks now occur high up the roof slope, affecting more insulation and aggravating the problem even more.

Permanent Solution to Ice Dam Problems

The best thing you can do to eliminate ice dams is to improve your attic ventilation and add / improve insulation to minimize heat loss. Insulation should be your first step, as poor attic insulation is the main cause of ice dams, and besides, you don’t want to keep wasting your money on heating up your unused attic. Seal the gaps between insulation, use expandable foam insulation for tight spots, etc. If you have the soffit vents/air intake slots, make sure that loose insulation does not block the air circulation.

Install proper ventilation. As mentioned before, soffit and ridge vent system is most effective, and does not cost a lot if you are having a new roof installed. You can also add it to an existing roof, but make sure there are appropriate conditions for adequate air circulation. Do NOT mix different ventilation systems – if you do so, there is a good chance that one system will minimize the effects of the other, therefore your ventilation will stop working.

What To Do If You Cannot Improve / Fix Ventilation and Insulation Issues

Although it is best to eliminate the source of the problem – heat loss and improper ventilation, it is not always a viable option for many homeowners, and another solution is required. As I discussed earlier, heat cables do not work and only increase your energy expenses. The best solution for a sloped roof is to have a Metal Roof installed.

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Metal roofs are designed to eliminated all damages associated with ice dams, by preventing the water from traveling upward. Be it a standing seam metal roof or an interlocking shingles system, Ice formations may occur, but the design of the roof will not let the melting water rise and penetrate the roof surface.

(Video) Roof Ice Dam | Secret to Prevent Roof Leaks

In fact, due to their smooth surface, metal roofs shed ice and snow, which comes down like an avalanche. To prevent this snow from damaging things below and falling on someone’s head, special Snow Guards must be used, which you can see in the image above.

For low slope roofs, we install an IB roofing system, which features hot-air welded seams to prevent water from entering the roof, and is perfect for residential low sloped roofing, as it comes with an asphalt shingle pattern to give it an architectural look and design.

To properly ventilate a low slope roof, we’ve created a special assembly method, which allows the installation of ridge vent, and eliminates associated roof leaks. We raised a ridge vent by 2 inches from the roof surface. This clearance is more than sufficient to prevent any water from entering your house through the ridge vent.

Ice Dams Prevention & Ventilation of Low-Slope Roofs (7)

In conclusion, I will once again mention that it is best to go to the source of the problem and fix as much ventilation and insulation as you can. Combine a great, energy efficient attic insulation with a permanent, cool flat or metal roof, and you will get a long lasting, great looking roof that will not leak, will save you money on roof repairs and heating / cooling costs, and take away many headaches of being a proud homeowner, as well as allow you to enjoy your home without ever worrying about roof leaks.

If you live anywhere in Massachusetts, Rhode Island or Connecticut, contact us to get a free roofing price quote and schedule a roof inspection and estimate to install a lifetime flat IB roof or a beautiful metal roof. You can also use our online roofing price calculator to estimate your roof replacement costs and annual energy savings.

References and Resources:

(Video) What Are Ice Dams and How Do You Prevent Them on Your Roof?

  • Flat Roof repair guide, which includes cost estimates for basic and advanced repairs, as well as what you can expect and how to choose a roofing contractor to fix your roof. Useful information for DIY homeowners, property maintenance personal and business owners.

There are: 30 Comments


FAQs

Ice Dams Prevention & Ventilation of Low-Slope Roofs? ›

Preventing Ice Dams on Roofs
  1. Remove Snow from the Roof. When you notice snow building up on your roof, it is advised to have it removed because this prevents ice dams from forming. ...
  2. Attic Insulation. This is one of the primary measures to help you prevent ice dams. ...
  3. Roof Ventilation. ...
  4. Examine Eavestroughs. ...
  5. Roof Inspection.
Nov 10, 2020

What is the best roof to prevent ice dams? ›

The truth is, the best solution for ice dams is removing the weak point – an asphalt shingles roof. It is the design and the way shingles are installed that make them prone to ice dam leaks. Shingles are a water shedding system, which means water runs down the roof, and in that case, shingles work.

How do you prevent ice buildup on gutters? ›

Install Helmet Heat in Your Gutters

The best option for a worry-free winter is to install gutter heaters to prevent ice dams. Gutter guards, such as Gutter Helmet, can stop any debris from clogging up your gutter system but can't always stop ice from forming.

What causes ice dams? ›

The snow on a roof surface that is above freezing will melt. As water flows down the roof it reaches the portion of the roof that is below 32F and freezes. This causes the ice dam. The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that average below 32F.

Does insurance cover ice dams? ›

Does homeowners insurance cover ice dams? The dwelling coverage of a homeowners policy may cover the cost to repair ice dam damage. That may include repairing your roof, walls, or other damage to the structure of your home up to your coverage limits. Damaged personal property may also be covered.

Do icicles mean Poor insulation? ›

"Icicles mean you're losing some heat and it also could mean you have poor ventilation in your attic," said Larsen and that's where his infrared camera comes into play. They can be used to show where heat is escaping a home. "Have someone take a look in your attic to see that your insulation is intact.

How do I keep ice dams off my roof without attic? ›

The key to curing ice dams is to make sure the temperature of your roof stays consistent with the eaves. To do this, prevent inside air from reaching attic or roof space by sealing any leaks.

What kind of salt is safe for roofs? ›

Sodium Chloride Or Rock Salt Or Halite

Since they are relatively inexpensive, they are the most preferred type of deicing salts. However, they work up to only 20 degrees Fahrenheit temperature and damage the freeze-induced expansion and contraction of the tiles and roof shingles.

Does roof raking prevent ice dams? ›

Using a long-handled roof rake to removing the snow from at least at lower 4 feet of roof edge can help prevent ice dams from forming. This is the only safe way to remove snow from a roof; never get onto a roof to remove snow in the winter.

Can I put salt in my gutters? ›

Consider salting your gutters

While you're up there, you can sprinkle sodium chloride into your gutters — but don't use the rock salt that you would spread on your sidewalks or driveways. Rock salt can damage your gutters, but sodium chloride can prevent ice from forming in the first place.

Should you knock down icicles from gutters? ›

Don't try to remove thick, long icicles from your gutters, experts say. You could wind up injuring yourself - falling chunks of ice are unpredictable - or damaging to your home. Leave them be, but keep an eye on them.

Can I put ice melt in my gutters? ›

Pantyhose and Ice Melt useful for gutters - YouTube

Can you put salt on your roof to melt ice? ›

A Do not put salt on your roof! Sodium chloride, or rock salt, is highly corrosive. It will damage the roofing, siding, gutters and downspouts, and the poisonous runoff will kill foundation plants and more. If you are going to try any homemade approach for breaking an ice dam, use deicer.

Do heat cables prevent ice dams? ›

First and foremost, it is very important to understand that heat cables do NOT prevent ice dams from forming or get rid of them altogether. They merely melt channels through the formed ice dams to minimize the amount of buildup and partially remove snow from the area.

Do gutters cause ice dams? ›

Contrary to popular belief, gutters do not cause ice dams. However, gutters do help to concentrate ice and water in the very vulnerable area at the edge of the roof. As gutters fill with ice, they often bend and rip away from the house, bringing fascia, fasteners, and downspouts in tow. Roofs leak on attic insulation.

Do ice dams damage shingles? ›

The answer to "can ice dams cause roof damage" is a resounding yes. Left untreated, ice dams can cause significant damage to your roof, shingles, and attic spaces. It's important to take steps to prevent ice dams from forming as well as remove snow from the edges of your roof.

How do I prevent ice dams on my flat roof? ›

Preventing Ice Dams
  1. Keep all drains, scuppers, gutters, and downspouts free of debris and vegetation that may restrict proper flow.
  2. Prune trees that may hang over the roof to prevent an accumulation of tree leaves and branches that may clog or slow roof drainage.
  3. Improve ventilation.
Feb 9, 2015

Does Allstate cover ice dam damage? ›

While dwelling coverage may help cover water damage cause by an ice dam, your policy likely won't pay for services to remove the ice dam. And again, even if a loss is covered, policy terms and limits will apply.

Why do some houses get icicles and others do not? ›

If your home has substantially more icicles than any homes near you, you may need to have your attic and insulation inspected. There are also common areas from which heat escapes, such as plumbing stacks, bathrooms, chimneys, dryer vents, and skylights.

Does attic insulation help with ice dams? ›

The most effective way to solve this problem is to insulate and air seal your home. This is one of the most effective insulation products to prevent ice dams. Most homes don't have enough insulation in the attic. Insulation helps keep the heat inside your home, which can reduce your heating bills.

How do I stop icicles from forming on my roof? ›

Here are some steps to preventing icicles from forming.
  1. Improve attic insulation. ...
  2. Seal leaks around fireplace flues, chimneys, and air-outtake vents. ...
  3. Make sure your attic is well-ventilated. ...
  4. Clean gutters before and between snowfall. ...
  5. Use a roof rake to remove snow a few feet from the eaves.

Are metal roofs better for ice dams? ›

Metal roofing can help but is not an ice dam panacea. A metal roof will generally shed snow better, but snow running down the roof will still freeze on the unheated overhangs, creating an ice dam. Metal roofing can be just as susceptible to this as any other roof.

Is a metal roof better for snow? ›

Metal provides durability, longevity, fire resistance, and its surface that prevents snow accumulation. It's an excellent roofing choice for the harsh winter elements that are experienced in snow country.

Can you use ice melt on a metal roof? ›

Additionally, some ice melt formulas can damage metal when used in large doses. If you have a shingle roof, stick to melts made from calcium chloride and avoid rock salt. If you have a good amount of metal on your roof, avoid products made from sodium chloride.

What can I put on roof to melt ice? ›

Use Warm Water

You will need an empty spray bottle and warm water. Put the warm water inside the bottle and spray it on directly to the ice formations until it melts. The idea is to melt the ice dams so that the roof and gutters can drain them like before.

Will a new roof prevent ice dams? ›

Fact: A new asphalt shingle roof with ice and watershield protection will not hold out water caused by ice dams. A new roof will most likely reduce water intrusion, but no matter how new the roof is, it is designed to shed water – not hold water. Myth: Ice dams cannot crack, unseal or damage roof shingles.

Do heat cables prevent ice dams? ›

First and foremost, it is very important to understand that heat cables do NOT prevent ice dams from forming or get rid of them altogether. They merely melt channels through the formed ice dams to minimize the amount of buildup and partially remove snow from the area.

Does roof raking cause ice dams? ›

THE CURE BECOMES THE CAUSE! best results when all of the snow can be removed from the roof. Only removing a portion of the snow can create problems further up - beyond any ice water barrier underlayments.

Where should ice guards be placed on a metal roof? ›

It is generally accepted all rows of snow guards should be placed on the lower half of the roof surface. The first row of snow guards is most often placed approximately 300 mm (12 in.) from the eave edge of the roof.

What kind of salt is safe for roofs? ›

The key is to avoid sodium chloride (or rock salt).

You should only use it on roofs in select circumstances like severe cold. If it's applied routinely, it can damage shingles, nails, eavestroughs, and other fittings. Look instead for de-icers incorporating safer materials like calcium chloride or potassium chloride.

Can I put calcium chloride on my roof? ›

A word of caution: Do not substitute rock salt for calcium chloride when trying to melt an ice dam, as sprinkling rock salt on roofs can damage shingles, and the runoff can kill bushes and foliage beneath. Make sure the ice-melt product you buy contains only calcium chloride, which is safe for shingles and vegetation.

Do roof pucks work? ›

Salt pucks and salt-filled pantyhose are unwise approaches to ice dam removal: They rarely work, and they damage your roof. (In fact, any form of DIY ice dam removal is unlikely to end well.)

Can I throw rock salt on my roof? ›

A Do not put salt on your roof! Sodium chloride, or rock salt, is highly corrosive. It will damage the roofing, siding, gutters and downspouts, and the poisonous runoff will kill foundation plants and more. If you are going to try any homemade approach for breaking an ice dam, use deicer.

Should you knock down icicles from gutters? ›

Don't try to remove thick, long icicles from your gutters, experts say. You could wind up injuring yourself - falling chunks of ice are unpredictable - or damaging to your home. Leave them be, but keep an eye on them.

Should you put salt in your gutters? ›

While you're up there, you can sprinkle sodium chloride into your gutters — but don't use the rock salt that you would spread on your sidewalks or driveways. Rock salt can damage your gutters, but sodium chloride can prevent ice from forming in the first place.

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4. DIY Ice Dams Prevention by @CoolFlatRoofing
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